Design evolution and verification of the general-purpose heat source

Abstract

y " ol work sponsored by an agency of the Ur> ted States Government nor any agency thereof nor any of their emp oyees makes any lumes any lega I abil ty or responsibil ty for thp accuracy comi-leteness reg ewnts ttiat is se would noi rDmmeic al p oduci process or M noi necessar ly consi States Gove ni process d ^closed This book was prepafd as an ai N( ther the Un ted States Govemmeni wirranty express or impi ed or as' usefu ness of any nformat on apparatus prodi ifrnge prvaiely owned rights Relerence here n to any spec t . ce ^-^ t ade name trademark manufacturer or oihe wisf does j,« oi m.u.v Its endorsement recommendation or favoring by the Un ted iny agency thereof The v ews and op n ons of authors expressed here n do not ir ly SI • ref e. th" Un ted States Government or any agency thereof .iM^mh^oiy^ DESIGN EVOLUTION AND VERIFICATION OF THE "GENERAL-PURPOSE HEAT SOURCE"

Light-Weight Radioisotope Heater Unit

“…The aeroshell side wall has an effective AIL ratio of 32.4 cm, and the two end walls have a combined AIL value of 10.1 cm. As reported by LANL, the free helium in the LWRHU occupies a volume of 0.723 cm 3 . The temperature dependence of the viscosity of helium is given by u (poise) = 1.29 x 10" 5 V 7(°K).…”

“…The problem in the GPHS case was eventually solved by using the CB CF insulator in an unloaded configuration, with the module components inside the insulator supported by integral stand offs [3]. The author therefore felt that a similar strategem would permit the use of CB CF insulation in the LWRHU, and proposed the alter native design pictured in Figure'28.…”

“…This was CB CF (Carbon B onded Carbon Fibers), a low density carbon carbon composite which is stable at very high temperatures and is much lighter and has an ap preciably higher thermal resistivity than pyrolytic graphite. For these reasons, it was selected as the insulator for the much larger GPHS (General Purpose Heat Source) modules [3], which power the current generation of Radioisotope Thermoelectric Generators [4,5]. And indeed, the CB CF insulated LWRHU designs proved to have significantly lower peak clad temperatures than the PG insulated designs.…”

Radioisotope Stirling Generator Options for Pluto Fast Flyby Mission

“…The study endeavored to employ the same General Purpose Heat Source (GPHS) modules that had been safety-qualified and flown on RTGs for the Galileo and Ulysses missions [Schock 1980] and that had also been used as the basis of the PFF RTG design options described in the preceding paper. The GPHS module design is depicted in Figure 3.…”

RTG Impact Response to Hard Landing During Mars Environmental Survey (MESUR) Mission

“…The study reported last year [3] presented two illustrative RTG designs: a 9-watt design for direct communication to Earth and a 3-watt design for communication through an orbiting relay. Both designs strove to maximize the use of previously developed technology, including the General Purpose Heat Source (GPHS) [4] used in the Galileo and Ulysses RTGs [5]; the SiGe thermoelectric materials employed in the RTGs for the Voyager, LES 8/9, Galileo and Ulysses missions, and the multicouples developed for DOE's Mod-RTG program [6,7]. Modifications were introduced only where necessary to improve the RTG's Impact resistance and to meet other mission requirements.…”